Automatic dryer control system



Jan. 9, 1968 J. R. HAWKINS 3,362,082

AUTOMATIC DRYER CONTROL SYSTEM Filed July 22, 1965 2 Sheets-Sheet 2 FIGS INVENTOR TAMES R. HAWKWS H45 ATTORNEY BYWWM United States Patent 3,362,082 AUTOMATIC DRYER CONTROL SYSTEM James R. Hawkins, Fern Creek, Ky., assignor to General Electric Company, a corporation of New York Filed July 22, 1965, Ser. No. 474,069 2 Claims. (Cl. 34-45) ABSTRACT OF THE DISCLOSURE A clothes dryer control system having an inlet thermostat in series with the dryer heater, which thermostat is closed below and open above a predetermined inlet air temperature, and an outlet thermostat responsive to the temperature of fabrics in the dryer. The outlet thermostat is in parallel wih the inlet thermostat, when the fabric temperature is below a predetermined level, and connects a timer in series with the inlet thermostat, when the fabric temperature is above the predetermined level, so that the timer reflects the accumulated time the dryer heater is energized after the fabrics reach a predetermined drying temperature.

Background of the invention Automatic clothes drying machines accomplish their drying function by tumbling clothes in a rotating drum while passing a stream of heated air through the drum. The simplest method of controlling the period of operation of such clothes dryers is by use of a timer which is effective to de-activate the dryer'after a predetermined period of operation. The substantial failing with prior art timer operated controls is that variations in ambient conditions may cause the time required to dry 21 load of clothes to vary substantially from one load to the next. Forthis reason many manufacturers have gone to expensive and 3,36Zfi8'2 Patented Jan. 9, 1968 after a predetermined period of timer operation. I provide a control circuit for controlling the dryer, including a first thermostatic means responsive to the temperature of air entering the chamber and arranged to control the heating means so as to maintain substantially constant the temperature of the air entering the chamber and a seccond thermostatic means responsive to the temperature of the fabrics in the chamber and arranged to connect the timer in the control circuit under the control of first thermostatic means only after the temperature of the fabric reaches a predetermined level.

The subject matter which I regard as my invention is particularly pointed out and distinctly claimed in the concluding portion of this specification. My invention, however, both as to organization and method of operation together with further objects and advantages thereof, may

best be understood by reference to the following descrip-- tion taken in conjunction with the accompanying drawings.

Brief description of the drawings FIGURE 1 is a side elevational view of a clothes dryer incorporating my improved dryer control circuit, the view being par'tly broken away and partly in section to illustrate details;

FIGURE 2 is a schematic illustration of one embodiment of my improved dryer control circuit used in the dryer of FIGURE 1; and

complicated control systems which attempt to sense the temperature of the clothes as they approach dryness and turn off the machine in response to a predetermined clothes temperature.

When drying clothes in domestic clothes dryers the clothes initially have a substantial amount of moisture available to be evaporated. Initially the heat input into a clothes dryer is effective primarily to raise the temperature of the clothes to an effective drying plateau, after which the temperature of the clothes remain relatively constant until virtually all of the moisture has been evaporated from the clothes. I have found that the variation in drying time caused by differences in ambient conditions occurs primarily in the period of time required to raise the temperature of the clothes to an effective drying level or plateau and that, for any particular load type, the length of dryer operating time required at the effective drying plateau is substantially the same regardless of variations in the ambient conditions.

It is accordingly an object of my invention to provide a simple and improved control system for a clothes dryer which utilizes a timed operation after the clothes temperature reaches an effective drying plateau.

More specifically it is an object of my invention to provide an improved, simple, timer operated control system for an automatic clothes dryer in which the timer operation is delayed until the temperature of the clothes" being dried reaches a predetermined level.

Summary of the invention FIGURE 3 is a schematic illustration of another embodiment of my improved dryer control circuit.

Description of the preferred embodiments Referring now to FIGURE 1, the machine illustrated is a domestic clothes dryer generally indicated by the numeral 1. Dryer 1 is provided in the usual way with a cabinet 2 having a front door 3 to provide access to the interior of the cabinet forloading and unloading clothes. Provided on the top wall 4 of the cabinet 2 is a control panel 5 which may, in the conventional way, include a suitable manual control '6 connected to a control assembly 7 mounted in panel 5. By manual presetting of control 6, the machine may be caused to start and automatically proceed through a cycle of operation.

Within cabinet 2, there is provided a clothes tumbling chamber, or drum, 8 mounted for rotation on a substantially horizontal axis. Drum 8 is substantially cylindrical in shape, having a first, center cylindrical wall portion 9, and second and third, outer cylindrical wall portions 10 and 11 located respectively adjacent an annular front wall 12 and a circular rear wall 13 of the drum. Wall portions 9, 10 and 11 are imperforate over their entire area so that the outer shell of the drum is imperforate. On the interior surface ofcylindrical wall portion 9 there may be provided a plurality of clothes tumbling ribs 14- So that clothes are lifted up when the drum rotates, and then tumble back down to the bottom of the drum.

The front of drum 8 may be rotatably supported within outer casing 2 by suitable idler wheels, one of which is indicated by the numeral 15. These wheels are rotatably secured on the top of a member 16 which extends up from base 17 of the machine. The wheels 15 are disposed beneath the drum in contact with portion 10 thereof so as to support portion 10 on each side to provide a stable support.

The rear end of drum 8 receives its support by means of a stub shaft 18 extending from the center of wall 13. Shaft 18 is secured Within a bearing 19 formed in a bafilelike member 20 which, in turn, is rigidly secured to the back wall 21 of cabinet 2 by any suitable means such as, for instance, by welding at a number of points 22. With the arrangement shown, the drum may rotate on a horizontal axis, with rollers 15 providing the front support and stub shaft 18 within bearing 19 providing the rear support.

In order to provide for the flow of a stream of drying air through the clothes drum, the drum is provided with a central aperture 23 defined by the front Wall 12 and a plurality of perforations 24 in rear wall 13. Perforations 24 in the present case are formed to extend around the rear wall in an annulus. The air provided to the drum is heated by a gas flame which issues from the outlet 25 of the conventional inshot burner 26. Burner 26 receives a regulated supply of gas from a solenoidoperated controlling valve assembly 27 of the type conventionally used in gas operated clothes dryers, the gas being supplied to the assembly 27 through a pipe or conduit 28 connected to an appropriate source (not shown) of gas. In the conventional way, primary air is drawn into the burner at te inlet end 29 thereof, the combustion occurs as a result of the mixture of this primary air with gas and its ignition by an appropriate pilot flame (not shown). The gas flame is then spread out, by a suitable member 30 positioned just outwardly of the outlet end of the burner, within a combustion chamber 31 so that secondary air is drawn in through end 32 of chamber 31 and is heated to a high temperature.

The outlet end 33 of chamber 31 communicates with an upwardly extending duct 34 which is provided with additional air openings 35, as needed, in order to reduce the temperature of the air and gas mixture to an appropriate extent. The heated mixture (hereinafter called heated air) then flows up through duct 34 and enters a generally circular heat diffuser chamber 36 formed between the member 20 and a baffle 37 which is rigidly secured to the outer surface of wall 13. Bafile 37 has openings 38 formed therein so that the heated air may flow from chamber 36 through openings 38 and perforations 24 into the drum 8. It readily will be observed that the combustion chamber 31, duct 34, chamber 36, openings 38, perforations 24 form an inlet conduit means for the heated air.

The front opening 23 of the drum is substantially closed by means of a stationary bulkhead generally indicated by the numeral 39. Bulkhead 39 is made up of a number of adjacent members including the inner surface 40 of the access door 3, a stationary frame 41 formed as a flange of front wall 42 of the cabinet, the inner surface member 43 of an exhaust duct formed by the cooperation of member 43 with the front wall 42 of the cabinet, and an annular flange 44 mounted on the frame 41 of front wall 42. It will be noted that a suitable clearance is provided between the inner edge of central aperture 23 and the edge of bulkhead 39 so that there is no rubbing between the drum and the bulkhead during rotation of the drum. In order to prevent a substantial air leakage through aperture 23 between the interior and exterior of the drum, a suitable ring seal 45, preferably formed of a felt-like material, is secured to flange 44 in sealing relationship with the exterior surface of drum wall 12. Central aperture 23 in addition to serving as part of the air flow path through the drum, also serves as a means whereby clothes may be loaded into and unloaded from the drum. Door 3, whose inner surface forms part of the bulkhead closing the opening, is mounted on cabinet 2 so that when the door is opened clothes may be inserted into or removed from the drum through the door frame 41. It will be noted that the door includes an outer flat imperforate section 46 and an inwardly extending hollow section 47 mounted on the flat outer section. Hollow section 47 extends into the door frame 41 when the door is closed, and the door surface 40, which comprises part of the combination bulkhead 39, is actually the inner wall of the hollow section. The air outlet from the drum is provided by a perforated opening 48 formed in the inner wall 40 of hollow door section 47. The bottom wall section of door 3 and the adjacent wall of door frame 41 are provided with aligned openings 49 and 50, opening 50 providing an entrance to a duct 51 formed by the cooperation of member 43 with front wall 42. As shown, a lint trap 52 is preferably positioned in the exhaust duct 51 and opening 50 and is supported by the door frame 41.

Duct 51 leads downwardly and communicates with a housing 53. Housing 53 contains a blower 54 which is directly driven by a motor 55. The blower draws heated air in from the duct 52 and then exhausts it from the cabinet 2 through an appropriate duct (not shown).

In addition to driving blower 54, motor 55 constitutes the means for effecting rotation of drum 8. In order to effect this rotation, motor 55 is provided with a shaft 56 having a small pulley 57 formed at one end thereof. A belt 58 extends around pulley 57 and also entirely around the cylindrical wall section 9 of drum 8. The relative circumferences of pulley 57 and wall section 9 cause the drum to be driven by the motor at a speed suitable to effect tumbling of the clothes therein. In order to effect proper tensioning of belt 58, there may be provided a suitable idler assembly 59 secured to the same support 60 which supports one end of the motor. Thus, the air is pulled through the drum at the same time the fabrics in the drum are tumbled. The air is heated by the flame emitted from the inshot burner 26, the heated air passing through the drum causes vaporization of moisture from the clothes. The vapor is carried off with the air as it passes out of the machine.

The operation of dryer 1 may be controlled by the new and improved control circuit shown in the schematic diagram of FIGURE 2. As shown therein, the control circuit includes supply conductors 63 and 64 adapted to be connected to a suitable source of electric power, for domestic use it will normally be a 110 volt power supply. Motor 55, connected between conductors 63 and 64, is a single-phase, induction-type motor having a main winding 65 and a start winding 66, both connected at a common end to a conductor 67. Through a conventional door switch 68 (which is closed when door 3 is closed and opened when the door is open), conductor 67 is connected to conductor 64.

The start winding 66 is connected in parallel with main Winding 65 under the control of a speed responsive device, such as that shown at 69, which is schematically shown as connected to the rotor 70 of the motor. The speed-responsive device 69 controls a switch 71 which is engageable with either a contact 72 or a contact 73, being engaged with contact 72 when the machine is at rest and moving into engagement with contact 73 as the motor comes up to speed. It readily can be seen that engagement with contact 72 connects the start winding 66 in parallel with main winding 65, while movement of switch 71 away from this position opens the start winding. Thus, as rotor 70 comes up to speed, the start winding becomes de-energized and the motor then continues to run on a main winding 65 alone.

Starting of the motor is provided by a manually operable switch 74 which, for instance, in the structure of FIGURE 1, may be moved to its closed position by pulling out on manual control 6. Switch 74 connects the motor to supply conductor 63 through contacts 75 and 76 of a switch 77, which also includes a third contact 78. Switch 74 is normally biased to the open position, as shown; however, when manual control 6 is pulled out, and provided switch 77 is closed, energization of the motor is provided. Within less than a second, under normal circumstances, the motor comes up to speed so that switch 71 engages contact 73. As a result of this movement of the centrifugally operated switch 71, the main winding 65 of motor 55 continues to be energized by the by-pass around switch 74 when manual control 6 is released and switch 74 opens. A timer motor 79 controls a cam 81 which, in turn, controls switch 77. Cam 81 also is movable by rotation of manual control 6, so that when operation of the machine is desired, manual control 6 may be rotated and cam 81 causes switch 77 to close all three of its contacts. The machine operation is terminated when cam 81 has been rotated sufiiciently by the timer motor 79 to open the contacts to switch 77.

Control of the heat provided by inshot burner 26 is accomplished by the following circuit. Starting at conductor 63, the circuit proceeds through contacts 76 and 78 of switch 77 and then through a conductor 82, an inlet thermostat 83, a conductor 84, a safety thermostat 85, a conductor 86, a solenoid 87 of control valve assembly 27, a conductor 88, and a speed responsive switch 89 to conductor 67. Thus, when contacts 76 and 78 of switch 77 are closed by manual control 6, and assuming that thermostats 83 and 85 and speed responsive switch 89 are closed, solenoid 87 will be energized to open control valve assembly 27 and supply gas to burner 26.

A parallel branch circuit is provided starting at conductor 82 and proceeding through a conductor 90, a contact 91 and movable arm 92 of an outlet thermostat 93 and a conductor 93a to conductor 84. Thus, it will be seen that, as long as movable arm 92 is in engagement with contact 91, solenoid 87 will be energized regardless of the position of inlet thermostat 83. As may be seen in FIGURE 1, inlet thermostat 83 is positioned in duct 34 so as to be responsive to the temperature of the heated air entering the dryer and outlet thermostat 93 is positioned in duct 51 to be responsive to the temperature of the air leaving the drum 8 (which is effectively the temperature of the clothes within the drum).

Outlet thermostat 93 also includes a contact 94 formed at one end of a conductor 95 having a contact 96 formed at the other end thereof. Contact 96 forms part of a timer operated switch having a second contact 98 and a movable arm 99 controlled by a cam 100 which, in turn, is driven by timer motor 79. Movable arm 99 is connected to timer motor 79 by a conductor 101 and timer motor 79 is connected to conductor 64 by a conductor 102. Thus, it will be seen that, when movable arm 92 of outlet thermostat 93 is in engagement with contact 94 and movable arm 99 of timer operated switch 97 is in engagement with contact 96, timer motor 79 is connected between conductor 84 and conductor 64. Contact 98 is connected to contact 75 by a conductor 103 so that, when movable arm 99 is in engagement with contact 98, timer motor 79 is connected between contact 75 and conductor 64.

A typical cycle of operation of the dryer under the direction of the control circuit shown in FIGURE 2 will now be explained. Assuming door switch 68 to be closed, thermostats 83 and 85 to be closed, movable arm 92 to be in engagement with contact 91 and movable arm 99 to be in engagement with contact 96; manual member 6 is rotated to cause cam 81 to close contacts 75, 76, and 78 of switch 77 and is then pulled out to close switch 74. Motor 55 quickly comes up to speed and causes speed responsive device 69 to close switch 89 and move arm 71 from engagement with contact 72 to engagement with contact 73 so that switch 74 is effectively bypassed and the motor will continue to run when manual member 6 is released.

The closing of switch 89 causes solenoid 87 to be energized to provide gas to inshot burner 26 which, in turn, causes the air entering the drum to be heated. The combustion of gas quickly causes the heated air entering the drum to reach the operating temperature of inlet thermostat 83 which opens; however, until the temperature of the clothes within the drum reaches the operating level or plateau, arm 92 of outlet thermostat 93 remains in engagement with contact 91 and solenoid 87 remains energized so that additional heat is continuously provided. When the temperature of the clothes or other fabrics within drum 8 reach the operating plateau movable arm 92 of outlet thermostat 93 moves away from contact 91 and into engagement with contact 94. Thereafter the energization of solenoid 87 will be under the control of inlet thermostat 83 alone. This is because the heat level provided by the cyclic operation of inlet thermostat 83 is sufficient to provide enough heat to maintain the clothes at the operating temperature level or plateau. Thereafter the dryer continues to operate with inlet thermostat 83 providing intermittent energization of solenoid 87 so that the inshot burner 26 is alternately energized and de-energized to maintain substantially constant the temperature of air entering the drum.

With movable arm 92 in engagement with contact 94, the timer motor 79 is eifectively connected in parallel with the solenoid 87 so that timer motor 79 runs when solenoid 87 is energized. This provides for accumulated timer run time which corresponds to burner on time. After a predetermined amount of timer run time timer motor 79 is eliective through cam to move arm 99 away from contact 96 and into engagement with contact 98 so that timer motor 79 is energized independently of inlet thermostat 83 and outlet thermostat 93. Shortly thereafter, for example, one minute, timer motor is efiective through cam 81 to open contacts 76 and 78 of switch 77 to de-activate solenoid 87. After an additional period of timer run time, for instance about three minutes, during which the temperature of the fabrics being dried is lowered to a comfortable handling level, timer motor 79 is effective to cause contacts 75 and 76 of switch 77 to be opened.

FIGURE 3 illustrates a second embodiment of my new and improved control circuit which is similar to the embodiment of FIGURE 2, but includingadditional switches which may be utilized to provide special cycles of operation. In the discussion of FIGURE 3 like numerals are used to identify elements which are the same as elements in the control circuit of FIGURE 2.

Referring now to FIGURE 3 it will be noted that inlet thermostat 83a, which will be positioned in the inlet duct 34 as is thermostat 83 of FIGURE 2, includes an arm 104 movable between a contact 105, formed at one end of conductor 84 and a contact 106. A manual switch 107 connects conductor 82 to conductor 103, a manual switch 108 connects conductor 82 to conductor 90 and a manual switch 109 is inserted in conductor 82 in series with inlet thermostat 83a. Conductor 101 and conductor 103 are connected by a branch circuit including a manual switch 110, which is in parallel with contact 98 and arm 99 of timer operated switch 97. Conductor 101 is connected to inlet thermostat contact 106 by a branch circuit including a manual switch 111. The various manual switches 107, 108, 109, and 111 may be opened and closed by any suitable manual means such as for instance by the rotation of manual control member 6 to a particular predetermined location.

In order to provide an automatic high speed dry setting contacts 75, 76 and 78 of switch 77 would be closed, manual switches 107, 110 and 111 would be opened and switches 108 and 109 would be closed. This may be accomplished by rotating manual control member to a first setting. With this setting the circuit is essentially the same as that shown in FIGURE 2 and the operation would be the same as described above.

For an automatic delicate dry operation, in which a lower temperature is desired so that the synthetic fabrics normally utilized in delicate goods such as ladies undergarments would not be harmed, manual control 6 would be rotated to another setting which would close contacts 75, 76 and 78 of switch 77 and close manual switch 109. At the same time it would cause manual switches 107, 108, 110 and 111 to be opened. With this circuit arrangement outlet thermostat 93 does not bypass inlet thermostat 83a and the solenoid 87 is under the sole control of the inlet thermostat 83a. This causes the air entering the drum to be limited to a lower temperature than in the automatic high speed drying setting. As the clothes in the drum approach dryness outlet thermostat 93 will trip and cause arm 92 to move into engagement with contact 94 so that the timer motor 79 is connected in parallel with the solenoid 87. In the automatic delicate dry setting a much shorter period of accumulated timer run time is used before timer motor 79 causes cam 100 to move arm 99 into engagement with contact 98 to provide operation of timer motor 79 independent of the thermostats. Thus, shortly after outlet thermostat 93 trips a cool-down period of approximately three minutes duration, is provided in a manner similar to the automatic high speed dry cycle, after which, cam 81 is effective to open all of contacts 75, 76 and 78 of switch 77 to turn off the machine.

In order to provide an automatic damp dry setting, in which the fabrics in the drum will still retain a considerable amount of moisture at the end of the drying cycle so as to be suitable for immediate ironing without sprinkling, manual switches 108 and 110 are opened and manual switches 107, 109 and 111 are closed. With this setting the inlet thermostat 83a is in sole control of the solenoid 87 and timer motor 79. Engagement of arm 104 with contact 105 energizes solenoid 87 to provide heat to the dryer and engagement of arm 104 with contact 106 de-energizes solenoid 87 and energizes timer motor 79. Thus, timer 79 is advanced alternately with operation of burner solenoid and after a predetermined period of timer motor run time cam 81 is effective to open contacts 75, 76 and 78 of switch 77. It will be noted that no timed cool-down occurs since manual switch 107 has been closed to bypass contacts 76 and 78. The alternate operation of solenoid 87 and timer motor 79 from the beginning of the cycle enables the same portion of the cam 81 as used for the automatic high speed drying setting to be used for the automatic damp dry setting.

In order to provide an air fluff without heat, manual switches 107, 108, 109 and 111 are opened and manual switch 110 is closed. With this setting, closing the contacts of switch 77 causes motor 55 to rotate and draw air through the drum 8 for a predetermined period of timer operation, after which timer motor 79 causes cam 81 to open the contacts of switch 77 and de-activate the dryer.

It will be obvious that, with only slight modifications, my new and improved control circuit may be adapted to control the operation of a dryer which has an electrically powered heater.

Thus, while in accordance with the Patent Statutes I have described what at present are considered to be the preferred embodiments of my invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is therefore aimed in the appended claims to cover all such variations as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A clothes dryer comprising:

(a) means defining a drying chamber to receive fabrics to be dried;

(b) means for circulating air through said chamber;

(0) heating means arranged to heat air entering said chamber;

{(1) a control circuit including timer means arranged to discontinue operation of said dryer after a predetermined period of timer operation;

(e) first thermostatic means connected in said circuit in series with said heating means, said first thermostatic means movable between an open position, normally to deenergize said heating means when the inlet air temperature is above a predetermined level, and a closed position, normally to energize said heating means when the inlet air temperature is below that predetermined level;

(f) second thermostatic means connected in said circuit and responsive to the temperature of fabrics in said drying chamber, said second thermostatic means being movable between a first position in parallel with said first thermostatic means, when the temperature of the fabrics is below a predetermined level, and a second position connecting said timer means in series with said first thermostatic means, when the temperature of the fabrics is above that predetermined level;

(g) whereby said heating means is energized continuously and said timer means is de-energized until the temperature of the fabrics in said chamber reach a predetermined level and, thereafter, said heating means is energized intermittently to maintain the inlet air temperature at about a predetermined level, with said timer means being energized concurrently with said heating means.

2. A clothes dryer as set forth in claim 1, further including manually operable switch means adapted to selectively connect said timer means in said control circuit independently of said first and second thermostatic means.

References Cited UNITED STATES PATENTS 3,238,636 3/1966 Chafee et a1. 3453 FREDERICK L. MA'I'PESON, 111., Primary Examiner.

JOHN J. CAMBY, Examiner. 

